1. Field of the Invention
The present invention relates to a cleaning robot having a carpet detector and a method of detecting a carpet boundary using the same and, more particularly, to a cleaning robot having a carpet detector and a method of detecting a carpet boundary using the same, in which the boundary of a carpet is detected to determine the area of the carpet.
2. Description of Related Art
Generally, robots have been developed for use in various industries as a part of factory automation. With the advancements made in automatic control and remote control techniques, robots have been widely used to perform tasks or repeated routine tasks in place of workers under extreme conditions such as at high and low temperatures, or in dangerous environments such as outer space and the bottom of the sea.
Recently, robots have been used for housework in homes or for custodial tasks offices, as well as industrial applications. A cleaning robot is an example of such robots.
Cleaning robots or automated cleaning robots have been developed, which automatically perform cleaning with minimal assistance or control from a user. In this respect, cleaning robots are required to uniformly clean a cleaning area and select a suitable cleaning mode in accordance with the material or the state of the floor of the area to be cleaned.
However, cleaning robots often have a problem with identifying their position and preparing a map of an area to be cleaned to effectively perform cleaning tasks. Also, cleaning robots have a problem with durability as they may be easily damaged due to frequent collisions with obstacles or falling over steps.
Particularly, if a cleaning mode is set when the material to be cleaned or the state of the floor is not recognized, cleaning quality may be varied depending on the state of the floor. For example, when a cleaning robot is in a mode suitable for the cleaning of a wooden floor and the floor of a given room is a wooden floor with carpet in the middle of the room, the cleaning robot can perform cleaning along the wooden floor by means of a proper sucking force. However, a driving wheel of the robot may sink into the carpet when the robot travels on the carpet.
If the driving wheel sinks into the carpet, the distance between the floor and a suction part of the robot becomes short, whereby a greater sucking force can be given to the carpet than the floor. Also, if the driving wheel sinks into the carpet, a seam of the carpet is sucked into the suction part of the cleaning robot. This may disturb suction of the robot. In other words, since the state and the material of the floor become main factors in suction of the cleaning robot, the cleaning robot is required to recognize the state or the material of the floor.
Studies of allowing a cleaning robot or a hand-operated cleaner to recognize a material of a floor have been discussed. Japanese Patent Publication No. 4-197327 discloses a method of identifying the presence of a carpet on a floor by sensing height variation of the floor using an infrared sensor. Korean Patent Publication No. 1992-0007588 discloses a cleaning robot having a supersonic transmitter and a supersonic receiver installed on a lower side to measure a distance using the transmission and reception times of supersonic waves for a predetermined period and recognize a step between a floor and a carpet using the measured distance. Korean Patent Laid-open Publication No. 2004-023420 discloses a cleaning robot provided with a plurality of infrared sensors to recognize a step part and perform cleaning by tracking a boundary of the step part.
As described above, to sense the carpet on the floor or recognize the step part, a plurality of infrared sensors or a supersonic sensor is provided. In this case, a problem occurs in that the manufacturing cost of the cleaning robot increases. Also, if the infrared sensor is exposed to strong light, the operational error may be generated. If the distance becomes short, the ultrasonic sensor may not operate normally.
Therefore, it is necessary to provide a cleaning robot that performs cleaning depending on types of the floor by simply sensing the presence of the carpet or the state of the floor without an expensive sensor.